Verify that the wiki displays a text string 'Table of contents'
Create a page in a wiki with text and headers. Add text and headers until the wiki automatically create a TOC
Search for the string on the Language customization page (or in AMOS, lang.moodle.org)

Michael de Raadt
added a comment - 17/Jan/12 11:44 AM Thanks for reporting this.
I've put that on the backlog.
In the meantime feel free to help us work on this issue. If you are able to provide a patch, please add a patch label so we will spot it.

Eloy Lafuente (stronk7)
added a comment - 01/Jul/12 4:03 AM Integrated (21, 22, 23 & master), thanks!
PS: Note 21_STABLE is already out of support so we are stopping bug fixes to land there along the next days...